#include <fstream>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;
ifstream F("poligon.in");
ofstream G("poligon.out");
#define x first
#define y second
#define st second.first
#define dr second.second
#define mid first
typedef pair<double,double> Pair;
typedef pair< Pair,pair<Pair,Pair> > Banda;
const int Nmax = 810;
const int Mmax = 60010;
int N,M,Co,Sol;
Pair Poly[Nmax];
int Point[Nmax];
#define make_band(A,B,C) ( make_pair(C,make_pair(A,B)) )
vector <Banda> Band[Nmax];
Pair Mid(Pair A,Pair B)
{
return make_pair( (A.x+B.x)/2 , (A.y+B.y)/2 );
}
Pair Int(Pair A,Pair B,Pair A2,Pair B2)
{
double a1 = A.y - B.y ;
double b1 = B.x - A.x ;
double c1 = - A.y * B.x + B.y * A.x ;
double a2 = A2.y - B2.y ;
double b2 = B2.x - A2.x ;
double c2 = - A2.y * B2.x + B2.y * A2.x ;
double X = a1*b2-a2*b1==0 ? -1 : (c2*b1-c1*b2) / (a1*b2-a2*b1) ;
double Y = b1==0 ? ( b2==0 ? -1 : (-c2-a2*X) / b2 ) : (-c1-a1*X) / b1 ;
if ( a1 == 0 )
{
Y = b1==0 ? -1 : -c1 / b1;
X = ( a2==0 || Y==-1 ) ? -1 : - ( b2*Y + c2 ) / a2;
}
return make_pair( X , Y );
}
int Find_band(Pair P,int Left,int Right)
{
if ( Left==Right )
return Left;
int Middle = ( Left+Right ) / 2;
if ( P.x >= Point[Middle] && P.x < Point[Middle+1] )
return Middle;
if ( P.x < Point[Middle] )
return Find_band(P,Left,Middle-1);
return Find_band(P,Middle+1,Right);
}
#define EPS 0.000001
int Ec(Pair P,Pair A,Pair B)
{
double a = A.y - B.y ;
double b = B.x - A.x ;
double c = - A.y * B.x + B.y * A.x ;
if ( P.x*a+P.y*b+c <= EPS && P.x*a+P.y*b+c >= -EPS ) return 0;
if ( P.x*a+P.y*b+c > 0 ) return 1;
return -1;
}
int Find_line(Pair P,int Pl,int Left,int Right)
{
if ( Right-Left==1 )
{
int Ecu=Ec(P,Band[Pl][Right].st,Band[Pl][Right].dr);
if ( Ecu==0 ) return 0;
if ( Ecu==1 ) return Right;
return Left;
}
if ( Left==Right )
return Left;
int Middle=(Left+Right)/2;
int Ecu=Ec(P,Band[Pl][Middle].st,Band[Pl][Middle].dr);
if ( Ecu==0 ) return 0;
if ( Ecu==-1 ) return Find_line(P,Pl,Left,Middle-1);
return Find_line(P,Pl,Middle,Right);
}
int main( void )
{
F>>N>>M;
for (int i=1;i<=N;++i)
{
double Cx,Cy;
F>>Cx>>Cy;
Poly[i]=make_pair(Cx,Cy);
Point[i]=Cx;
}
Poly[N+1]=Poly[1];
sort(Point+1,Point+N+1);
Co=1;
for (int i=2;i<=N;++i)
{
if ( Point[i]==Point[i-1] ) continue;
Point[++Co]=Point[i];
}
for (int i=Co+1;i<=N;++i) Point[i]=0;
for (int i=1;i<Co;++i)
{
Pair A,B,C,D;
for (int j=1;j<=N;++j)
{
A = Int(Poly[j],Poly[j+1], make_pair(Point[i],0), make_pair(Point[i],Mmax) );
B = Int(Poly[j],Poly[j+1], make_pair(Point[i+1],0), make_pair(Point[i+1],Mmax) );
C = Poly[j];
D = Poly[j+1];
if ( A.x > B.x || (A.x==B.x && A.y > B.y) ) swap(A,B);
if ( C.x > D.x || (C.x==D.x && C.y > D.y) ) swap(C,D);
int Ok=0;
if ( (A.x > C.x && A.x < D.x) || (B.x > C.x && B.x < D.x) ) Ok=1;
if ( A.x == C.x ) Ok=1;
if ( B.x == D.x ) Ok=1;
if ( !Ok ) continue;
Band[i].push_back( make_band( A,B,Mid(A,B) ) );
}
sort(Band[i].begin(),Band[i].end());
}
/*while ( M-- )
{
Pair P;
F>>P.x>>P.y;
if ( P.x < Point[1] || P.x > Point[Co] ) continue;
int Pl = Find_band( P , 1 , Co-1 );
int Val = Ec(P, Band[Pl][0].st, Band[Pl][0].dr );
if ( Val==0 || Val==-1 )
{
if ( Val==0 ) ++Co;
continue;
}
int Nbr = Find_line( P , Pl , 0 , int(Band[Pl].size())-1 );
Sol+=1-(Nbr%2);
}
G<<Sol<<'\n';*/
}